Where have all the saguaros gone?

Because the saguaro blossom is the state flower and the giant cactus is a tourist attraction, Arizona has a vested interest in finding what may be killing the plant.

By examining photographs taken in 1935, researchers determined that saguaro forests have been reduced by up to 75 percent. And many of the remaining cacti are afflicted with “brown decline,” a condition in which the natural green color darkens.

One theory is that pollution caused the decline of the saguaros. Researchers are looking for signs of damage from increased automobile-exhaust fumes that came with Arizona’s postwar population boom.

Another theory involves bats. Near one forest, a tourist concessionaire commandeered a cave for his business. The cave was a roosting place for Sanborn bats, which cross-pollinate saguaros; ridding the cave of bats disrupted the pollination pattern in that area. There is hope for the plants; some new seedlings are taking root. But patience is needed: saguaros, which live for 150 to 250 years, take half a century to reach maturity.